(60/21.5)*(18) = 50.23 . . . answer is likely 50 feet tall
From the setup of the problem, the "length of the top of the bookcase, measured along the attic ceiling" will be the hypotenuse of a right triangle, the length "AB". We have both the angle between AB and AC and the length of AC (3.24 meters), so we can use trigonometric identities.
The cosine of the 40 degree angle between AB and AC is equivalent to the length of AC divided by the length of AB. Equivalently, we have:

where "h", the hypotenuse, is the length we want. Rearranging the formula to solve for h we have that

which is 4.2295... meters. Converting to centimeters (multiplying by 100) we have that h = 422.95... centimeters, or if we round the value, h = 423 centimeters.
True. The formula for the area of a rectangle is length multiplied by width. Therefore, we can find the width by dividing the area by the length through Division Property of Equality.
Hmm, let's see. Well a triangle's dimensions add up to 180. If both sides given add up to 14. Simply subtract 180 by 14. You get, 166. If I'm wrong, feel free to correct me on that :)